MM-55192: Fix datepicker hand on DST dates (#28694)

webapp/channels/src/components/custom_status/date_time_input.test.tsx

@@ -12,7 +12,7 @@ import * as i18Selectors from 'selectors/i18n';
 
 import mockStore from 'tests/test_store';
 
-import DateTimeInput from './date_time_input';
+import DateTimeInput, {getTimeInIntervals} from './date_time_input';
 
 jest.mock('selectors/i18n');
 
@@ -34,4 +34,17 @@ describe('components/custom_status/date_time_input', () => {
         );
         expect(wrapper.dive()).toMatchSnapshot();
     });
+
+    it.each([
+        ['2024-03-02T02:00:00+0100', 48],
+        ['2024-03-31T02:00:00+0100', 46],
+        ['2024-10-07T02:00:00+0100', 48],
+        ['2024-10-27T02:00:00+0100', 48],
+        ['2025-01-01T03:00:00+0200', 48],
+    ])('should not infinitely loop on DST', (time, expected) => {
+        const timezone = 'Europe/Paris';
+
+        const intervals = getTimeInIntervals(moment.tz(time, timezone).startOf('day'));
+        expect(intervals).toHaveLength(expected);
+    });
 });

webapp/channels/src/components/custom_status/date_time_input.tsx

@@ -40,14 +40,21 @@ export function getRoundedTime(value: Moment) {
     return start.add(remainder, 'm').seconds(0).milliseconds(0);
 }
 
-const getTimeInIntervals = (startTime: Moment): Date[] => {
+export const getTimeInIntervals = (startTime: Moment): Date[] => {
     const interval = CUSTOM_STATUS_TIME_PICKER_INTERVALS_IN_MINUTES;
     let time = moment(startTime);
     const nextDay = moment(startTime).add(1, 'days').startOf('day');
+
     const intervals: Date[] = [];
     while (time.isBefore(nextDay)) {
         intervals.push(time.toDate());
+        const utcOffset = time.utcOffset();
         time = time.add(interval, 'minutes').seconds(0).milliseconds(0);
+
+        // Account for DST end if needed to avoid displaying duplicates
+        if (utcOffset > time.utcOffset()) {
+            time = time.add(utcOffset - time.utcOffset(), 'minutes').seconds(0).milliseconds(0);
+        }
     }
 
     return intervals;
@@ -113,7 +120,7 @@ const DateTimeInputContainer: React.FC<Props> = (props: Props) => {
 
     const handleTimeChange = useCallback((time: Date, e: React.MouseEvent) => {
         e.preventDefault();
-        handleChange(moment(time));
+        handleChange(timezone ? moment.tz(time, timezone) : moment(time));
         focusTimeButton();
     }, [handleChange]);